Hi Peter,
Here is a bit of doc about that util_memoize thingy.
https://openacs.org/doc/server-cluster.html
Also you can look at the /admin/site-map of your OpenACS under ACS Kernel in section server-cluster.
Based from our load of our servers. Normally aolserver, OpenACS, PG, etc only needs memory to be fast. Not much CPU util. RAID 5 will always be the slowest among RAIDs due to the computation overhead which is made signicantly low by the hardware RAID. RAID 1 is good for reads but bad for writes since you have to write twice. Also RAID 1 is a waste of space. RAID 0 is good on read and write at the expense of less reliability.
If you will use a web farm then those web farm does not need any fast I/O as long as they have enough RAM to cache the files. Since its a web farm you don't need the realiablity, so RAID 0 is very much preferred. Redundancy is taken cared of in the machine level rather than the hard disk level. For the db server a fast I/O (10K or 15K rpm disks, with as much RAM on the RAID controller) is a must, also a reliable storage. RAID 0+1 is a good one if you have the money. But normally I just pick RAID 1 since reliability for me is higher on the list than performance. There is also less likely that such a site will ever tax today's hardware. Unless your site is really really big there is not much in buying the greatest hardware. Just buy what is easy to administer and reliable. Not much worries about performance.
Oh yeah, if you go for a web farm its better to have them mount their OpenACS to a central server. Most likey this will be the db server. That way when you update the sources of the web farm you just update it on one copy.
